Constructing a Biphasic Electronically Locked Chain to Inhibit Na‐Dendrite Towards High‐Performance Solid‐State Sodium Batteries

ABSTRACT Solid‐state sodium metal batteries offer substantial advantages in resource sustainability and cost effectiveness bsesides safety, making them promising candidates for next‐generation energy storage technologies. However, the intrinsic electronic conductivity of Na 3 Zr 2 Si 2 PO 12 (NZSP) electrolyte facilitates Na‐ion reduction within the electrolyte, resulting in Na dendrite formation. Conventional interface modifications inadequately suppress the interfacial electron transport, further accelerating the dendrite growth and largely compromising electrochemical stability. This work effectively suppresses sodium dendrite growth by constructing a biphasic electronically locked chain. Na 3 AlF 6 incorporation into NZSP at the bulk level enhances the ionic conductivity while suppressing the electronic conductivity. At the interface level, SnBr 2 coating reacts with metallic Na to in situ form NaBr, creating an effective electron‐blocking barrier. This integrated approach enables the symmetric cells to achieve exceptional cycling durability (9000 h at 0.2 mA cm −2 ). Full cells assembled with Na 3 V 2 (PO 4 ) 3 cathodes demonstrate superior electrochemical performance (92.26%@2000 cycles at 1C and 90.01%@1000 cycles at 2C). This strategy of bulk‐interface electron suppression addresses fundamental challenges in solid‐state sodium batteries, providing a practical pathway toward developing long‐life solid state sodium metal batteries with enhanced safety features.